This invention relates generally to an electrostatographic copier or printer, and more particularly, concerns a cleaning apparatus. In an electrophotographic application such as xerography, a charge retentive surface (i.e. photoconductor, photoreceptor or imaging surface) is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (i.e. an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g. paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. This process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charge surface may be imagewise discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operates similarly.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a brush with soft conductive fiber bristles or with insulative soft bristles which have suitable triboelectric characteristics. While the bristles are soft for the insulative brush, they provide sufficient mechanical force to dislodge residual toner particles from the charge retentive surface. In the case of the conductive brush, the brush is usually electrically biased to provide an electrostatic force for toner detachment from the charge retentive surface. Toner particles adhere to the fibers (i.e. bristles) of the brush after the charge retentive surface has been cleaned. The process of removing toner from these types of cleaner brushes can be accomplished in many ways. Typically, brush cleaners, use flicker bars to provide the detoning function. A flicker bar is usually a thin long bar with a controlled amount of interference with the brush fibers. When the fibers encounter the flicker bar, the fibers bend and the impact dislodges toner particles adhering to the fibers. Once released, these particles may be carried away by an airstream to a toner filter or separator. The disadvantage of this method is that the brush fibers have just one chance or revolution for detoning. This results in partial detoning of the fibers and a gradual accumulation of toner in the brush. When the amount of toner accumulated in the brush exceeds a critical level, a severe cleaning failure can occur.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
Research Disclosure Bulletin, December 1975, No. 14033, page 43, "A Half Tone Screen Cleaning Device" discloses a rail and a screen member which define a slot with a brush member mounted slidably therein. Actuation of a drive motor reciprocates a shaft which reciprocates a brush across the screen member removing particle contaminants therefrom.
U.S. Pat. No. 4,054,381 to Bernhard, discloses a spiral brush mounted for rotation on a shaft centrally located within a housing and a stationary open mesh screen coaxially located with respect to the shaft having a small space being provided between the brush fibers and the screen. Rotation of the spiral brush operates to sift toner through the screen to the outlet of the filter housing while concurrently moving the toner from the input opening toward the discharge opening.